At this stage, the patient is normally given only six to 12 months to live.

Chemotherapy based on a drug called mitoxantrone can be used to relieve pain, but it does not prolong survival.

Doctors should now consider docetaxel for patients with prostate cancer where the disease is no longer responsive to hormone therapy.

Professor Malcolm Mason from Cancer Research UK

The two docetaxel studies involved nearly 1,800 men with advanced prostate cancer.

Professor Nick James, professor of clinical oncology at UK's University of Birmingham and author of one of the studies, said: "These results are groundbreaking for men with prostate cancer resistant to hormone therapy.

"Prior to docetaxel, no drug has ever shown a survival benefit for men with hormone resistant prostate cancer.

"These results completely alter the standard treatment paradigms for the disease and pave the way for further studies."

In his study, men given docetaxel every three weeks survived for an average of 18.9 months compared to 16.5 months among men given standard care with mitoxantrone.

In the second study, a similar survival benefit was seen with docetaxel compared with mitoxantrone - 17.5 months compared with 15.6 months, respectively.

The men who received docetaxel in these studies experienced more side effects, such as nausea and hair loss, but said their overall quality of life had improved.

Availability

Chris Hiley from the Prostate Cancer Charity said: "This is progress and we welcome it unreservedly.

"However, such powerful drugs are not without side effects so perhaps not all men will choose to have this treatment.

"But it is certainly an advance as men, who have exhausted all other treatments, now have a new option to consider.

"Further research will doubtless reveal ways of improving this treatment and even more progress on survival can be expected in the future."

Professor Malcolm Mason from Cancer Research UK said: "This is the first time chemotherapy has been shown to lengthen the lives of prostate cancer patients.

"Although the drug combinations used led to greater toxicity than many treatments in current use, most of the resulting side effects are easy to manage.

"In fact, the toxicity observed in the study was no worse than one would expect from many chemotherapy drugs that are widely used to treat cancers such as breast cancer.

"Encouragingly, the new drug combinations improved patient quality of life as well as survival.

"Doctors should now consider docetaxel for patients with prostate cancer where the disease is no longer responsive to hormone therapy."

Docetaxel, which is produced by Aventis, is licensed for use in advanced breast and lung cancer.

In September, the Committee for Medicinal Products for Human Use advised the European Agency for the Evaluation of Medicinal Products that the drug could be used for advanced prostate cancer.